Ignitron construction



1942- D. E. MARSHALL EE'AL 2,291,973

IGNITION cous'rnucnon Filed Oct. 9, 1940 INVEN TOR .51 E". MfiEV/WLZBYZQZ/VOCf/EZ ATTO R N EY Patented Aug. 4; 1942 2,291,973 IGNITRONCONSTRUCTION Allwood, and William J.

Donald E. Marshall, Knochel, Irvington,

. 3., assixnors to Westinghouse Electric & 'Manll! act Company,

East Pittsburgh, Pa., a corporation oi Pennsyl- Application October 9,1940, Serial No.

2 Claims. (01. 250-275) Our invention relates to discharge devices andmore particularly to the type of discharge device known as sealed-offignitrons.

An object of our invention is to simplify the arrangement and materialof the metal casing of a sealed-off ignitron so that the device willoccupy a very small space.

Another object of the invention is to modify the anode structure toeliminate breaking of the .anodes.

Other objects and advantages of the invention will be apparent from thefollowing description and drawing in which:

Fig. 1 is a view in cross section of a device embodying our invention.

Fig. 2 is a top elevational view of Fig. 1.

Fig. 3 is a cross section on lines III-III of Fig. 1.

Sealed-off ignitrons such as disclosed in Patent 2,140,369, issuedDecember 13, 1938, in the name of D. E. Marshall, have occupiedconsiderable space and the structure has also utilized considerablematerial.

It is an object of our invention, as mentioned above,-to simplify thecasing so that the device will occupy a very small space. In simplifyingthe casing and reducing the dimensions of the electrodes, we havediscovered that the effect on the prior art structure is a tendency tocrack the carbon anode usually employed in these devices. Our inventionalso includes modifying the anode structure to eliminate this crackingof the carbon anode.

In Fig. 1 we have disclosed the cylindrical casing l0, preferably ofstainless or cold-rolled steel, having an inverted cap-shaped bottomheader ii welded therein. The cap-shaped header, in combination with theadjacent casing, supports the mercury pool l2. A tubulation 33 extendsthrough the bottom portion of the casing and this tubulation ispreferably of a non-corrosive metal such as nickel.

This'tubulation has a flange M with an eyelet l5 welded thereto. Theflange M is welded to the top of the header ll after the tubulation 63has been inserted through the opening it in. this header. After theassembled tube has been heattreated and exhausted, the tubulation isclosed off at the tip 51. If desired, a solder 18 may enclose thistubulation and be surrounded by a protecting non-corrosive cap i9 suchas brass. The casing i0 may be flanged out at the upper por tion thereofat for the purpose of support or for suitable attachment to awater-cooling jacket, or to an air-cooling arrangement, as desired.

We preferably weld a cylinder 2| to the upper interior wall of thecasing Hi. This cylinder 2! is of an iron-nickel-cobalt alloy sold underthe trade name of Kovar. To the other edge of this cylinder is sealed acylinder of insulating material 22 preferably of borosilicate glass. Atthe other end of this cylinder is sealed a cap 23 likewise of theiron-nickel-cobalt alloy sold under the trade name of Kovar.

The cap 23 in place of having a closed end has an integral upwardlyextending cylindrical stem portion 24. This stem portion 24 is in turnsealed to a cylindrical borosilicate glass portion 25 that in turn issealed to a perforated cylindrical cap 26, also of the alloy metal soldunder the trade name of Kovar. Through the central perforation of thiscap 26 extends a long ignitor stand ard 21 which may be of steel. Thisstandard at 28 has an enlarged portion that is welded to the bent-inflange 29 of the cap 26. At the lower end of the standard 21 is atapered tip 30 of a high resistance material, such as boron carbide,dipping into the mercury pool l2. The upper end of the standard has anenlarged portion 3| to which may be connected a flexible connector to asource of electricity for igniting the device.

To the underside of the cap 23 is welded a cylinder 32, preferably ofsteel, extending down- Wardly to the location of the anode 33 which isof carbon. In the prior art such a tubular metal connection was screwedto the carbon anode. It will be noted that the heat applied to thesealing operation of the borosilicate glass 25 and the cap 23, as Wellas the heat applied to the sealing of the glass 22 to the cap 23, has agood conductive path through this cylindrical member 32 to the carbonanode 33 in these devices of the prior art.

It will be noted that the diameter of the easing iii and the diameter ofthe carbon anode 33 are greatly reduced over the diameter of the casingand anode in Patent 2,140,369. The result of the transfer of heat from ametal cylinder to the anode to which it was directly screwthreadedcaused an uneven expansion of the two connected devices and cracksresulted in the anode. In order to prevent this, we utilize anintermediate sleeve 34 which is directly connected by screw threads tothe cylindrical member 32 and then in turn is attached to the anode 33by screw threads. Ihere is a slight space 35 between the bottom portionof the cylindrical member 32 and the top of the anode 33. The conductionof heat is accordingly cut down before it reaches the anode by theboundary between the "nickel-cobalt and cylindrical member 32 and thesleeve 84, as well as the intervening space 8| between the anode and thecylindrical member 82.

The cap member I! may be made of very thin material and we preferablycopper solder a steel member iitothetop ofthiscap ll. Onthis additionalmember 38 we preferably silversolder athick ring 81 of copper which ispreferably, screw-threaded on its inner side 38, and a cylinder member30 preferably of copper is attached bysimilarscrewthreadstothisringll.This cylinder member 3! preferably rises to a height to protect thesmall glass cylinder 25 and the thin cap 20 sealed thereto, and alsoacts as an electrical connection for the anode 88.

The reason for these various solders is that the iron-nlckel-cobaltalloy cannot be used with silver, and the copper solder cannot be usedwith copper. We desire the cap to be made of irontheringll tobeofcopper. It will be noted that we have simplified thelllmaybeassmallaslyfi inches.

small diameter can effectively carry current having i000 amperes peakand 25 amperes average. It will also be noted that in spite of thereduction of the diameter of the casing and the diameter of the anode,we have greatly strengthened the anode structure over that disclosed inthe prior art. We have also made the tubuiation and its protection ofnon-corrosive material so that there will be no danger of leakagetherethrough by an accumulation of corrosion.

It is apparent, however, that many modifications may be made in thepreferred embodiment disclosed, and accordingly we desire only suchlimitations to be imposed upon our invention as are necessitated by thespirit and scope of the following claims.

We claim: I

i. In a discharge device, a plurality of cylindrical members the bodyportions whereof are substantially of equal diameter and sealedsuccessively to each other one above another thereby providing anelongated cylindrical chamber of substantially the same size throughoutthe length intermediate one of said members comprising insulatingmaterial and the others being of metal. a bottom header for the lowerend of said chamber sealed with respect to the lowermost one of saidmembers. the uppermost of said members comprising a cap having a rethatthe diameter of g and having a duced hollow neck portion projectingupwardly therefrom, a cylinder axially of said chamber depending fromsaid same entirely through the member next below said cap, an anodeimmediately below said depending cylinder. said anode and cylinderhaving adjacent portions of equal diameter and screw threaded, a sleevehaving interior threads throughout its length engaging the threads ofboth the depending cylinder and anode, said sleeve being of relativelythin metal and tending to stop heat conduction between said dependingcylinder and anode. an ignition standard depending from above said neckto the proximlty of, said header and having a tip on the lower endthereof, and a pool cathode in said chamber into which said till 619 2.In "a discharge device, a plurality of cylindrical members the bo yportions whereof are substantially of equal diameter and sealedsuccessively to each other one above another thereby providing anelongated cylindrical chamber of substantially the same size throughoutthe length thereof, an intermediate one of said members comprisinginsulating material and the others being of metal, a bottom header forthe lower end of said chamber sealed with respect to the lowermost oneof said members, the uppermost of said members comprising a cap having areduced hollow neck portion projecting upwardly therefrom, an uppercylindrical insulating member sealed to the upper end of said neckdiameter throughout its length substantially that of the said neck, acylinder axially of said chamber depending from said cap within the bodyof the same entirely through the member next below said cap, an anodeimmediately below said depending cylinder, said anode and cylinderhaving adjacent portions oi equal diameter and screw threaded, a sleevehaving interior threads throughout its length engaging the threads ofboth the depending cylinder and anode, said sleeve being of relativelythin metal and tending to stop heat conduction between said dependingcylinder and anode, an ignition standard depending from above said upperinsulating member to the proximity of said header and having a tip onthe lower end thereof, and a pool cathode in said chamber into whichsaid tip dips.

DONALD E. MARSHALL- WILLIAM J. KNOCHEL.

capwithinthebodyofths'

